1. Field of the Invention
This invention relates to a speaker system and a cooling device therefor.
2. Description of the Related Art
Conventionally, a sound system for automobile use and the like has been actively high-powered, and accordingly, heat dissipation of the speaker system has been increasingly important. FIGS. 1A and 1B are diagrams each showing the construction of a conventional speaker. The construction of the speaker 10 will be briefly described with reference to these figures. FIG. 1A is a cross-sectional view showing essential parts of the speaker 10. FIG. 1B is a cross-sectional view showing essential parts of the speaker 10 to which a cooling device 11 is attached.
Speaker 10 has a magnetic circuit including a disk-shaped bottom yoke 1 formed of a magnetic metal member and having a hollow cylindrical pole portion la, an annular magnet 2 placed on the bottom yoke 1, and an annular top yoke 3 formed of a magnetic metal member and placed on the magnet 2. Further, a diaphragm 7 with a dust cap 7a arranged at a center thereof is suspended on a frame 4 via an edge 5 and a damper 6, and joined to a coil bobbin 9 having a voice coil 8 wound therearound. The coil bobbin 9 is arranged in a magnetic gap formed by the magnetic circuit.
The magnetic circuit has a magnetic path (indicated by arrows in the figures, for instance) formed by the bottom yoke 1, the top yoke 3, and the magnet 2. A gap between an end of the pole portion la and the top yoke 3 forms the magnetic gap for collecting the magnetic flux of the magnet 2 and thereby generates a high-density uniform magnetic field. When a drive current is supplied to the voice coil 8 through a power amplifier circuit, not shown, the coil bobbin 9 arranged in the magnetic gap with predetermined spaces from the pole portion la and the top yoke 3 is actuated to perform a reciprocating motion by an electromagnetic force generated in the magnetic gap. The reciprocating motion is transmitted to the diaphragm 7 whereby sounds are emitted. In short, an electrical signal is converted to acoustic vibrations. In the case of speaker 10, especially when a large drive current is continuously supplied, the voice coil 8 generates Joule heat to thereby increase the temperature of the whole magnetic circuit formed by the bottom yoke 1 and its associated components.
To eliminate the above inconvenience, it is possible to employ a method of fitting a cooling device 11, which is formed by a disk-shaped member highly efficient in thermal conductivity, with a concentric groove formed therein, in the pole portion la of the bottom yoke 1. That is, if the cooling device 11 formed with the groove in which the disk-shaped bottom yoke 1 can be fitted is used, heat from the magnetic circuit can be emitted simply by mounting the device 11 on the bottom yoke 1 of the speaker 10, as shown in FIG. 1B.
However, heat generated by the voice coil 8 is gradually transferred to the bottom yoke 1 and the top yoke 3. Therefore, it takes time before the heat generated by the voice coil 8 is accumulated in the bottom yoke 1 and the top yoke 3, which prevents effective transfer of heat from the voice coil 8 to the cooling device 11.
The invention has been made in view of the above problems, and it is an object of the invention to provide a speaker system and a cooling device therefor which are capable of effectively dissipating heat generated by a voice coil.
To attain the above object, according to a first aspect of the invention, there is provided a speaker system including a magnetic circuit having a magnetic gap, a voice coil arranged in the magnetic gap, and a diaphragm attached to the voice coil, the voice coil and diaphragm being driven by supplying a drive current to the voice coil, comprising a first member arranged adjacent to the voice coil and inside a magnetic flux loop generated by the magnetic circuit, a second member arranged outside the magnetic flux loop generated by the magnetic circuit, and a third member connecting the first member and the second member to each other, wherein the first to third members are formed of a material excellent in thermal conductivity.
Preferably, the magnetic circuit is of an outer magnet type.
Preferably, the magnetic circuit is of an inner magnet type.
To attain the above object, according to a second aspect of the invention, there is provided a cooling device for a speaker system, comprising a first member arranged adjacent to a voice coil and inside a magnetic flux loop generated by a magnetic circuit, a second member arranged outside the magnetic flux loop generated by the magnetic circuit; and a third member connecting the first member and the second member to each other, wherein the first to third members are formed of a material excellent in thermal conductivity.
Preferably, heat generated in the voice coil is transferred to the second member via the first member and the third member to thereby allow the heat to be dissipated from the second member.
Preferably, the first to third members are integrally formed as a unitary member.
According to the speaker system and the cooling device therefor, the first member is arranged adjacent to the voice coil and at the same time inside the magnetic flux loop generated by the magnetic circuit, and the second member is arranged outside the magnetic flux loop, with the third member connecting the first member and the second member. Further, the first to third members are formed of a material excellent in thermal conductivity. Therefore, heat generated by the voice coil is transferred in the order of the first member, the third member, and the second member, thereby being dissipated from the second member.